Drug delivery systems for disease treatment which introduce active ingredients into the circulation are numerous and include oral, transdermal, inhalation, subcutaneous and intravenous administration. Drugs delivered by inhalation are typically delivered using positive pressure relative to atmospheric pressure in air with propellants. Such drug delivery systems deliver drugs as aerosols, nebulized or vaporized. More recently, drug delivery to lung tissue has been achieved with dry powder inhalers. Dry powder inhalers can be breath activated or breath-powered and can deliver drugs by converting drug particles in a carrier into a fine dry powder which is entrained into an air flow and inhaled by the patient. Drugs delivered with the use of a dry powder inhaler are no longer only intended to treat pulmonary disease, but can also be absorbed into the systemic circulation so they can be used to treat many conditions, including, but not limited to diabetes and obesity.
Dry powder inhalers, used to deliver medicaments to the lungs, contain a dose system of a powder formulation usually either in bulk supply or quantified into individual doses stored in unit dose compartments, like hard gelatin capsules or blister packs. Bulk containers are equipped with a measuring system operated by the patient in order to isolate a single dose from the powder immediately before inhalation. Dosing reproducibility requires that the drug formulation is uniform and that the dose can be delivered to the patient with consistent and reproducible results. Therefore, the dosing system ideally operates to completely discharge all of the formulation effectively during an inspiratory maneuver when the patient is taking his/her dose. However, complete discharge is not generally required as long as reproducible dosing can be achieved. Flow properties of the powder formulation, and long term physical and mechanical stability in this respect, are more critical for bulk containers than they are for single unit dose compartments. Good moisture protection can be achieved more easily for unit dose compartments such as blisters. However, materials used to manufacture blisters allow air into the drug compartment and subsequently formulations can lose viability with long storage. Additionally, dry powder inhalers which use blisters to deliver a medicament by inhalation can suffer with inconsistency of dose delivery to the lungs due to variations in the air conduit architecture resulting from puncturing films or peeling films of the blisters.
Dry powder inhalers in the art can generate drug particles or suitable inhalation plumes during an inspiratory maneuver by deagglomerating the powder formulation within a cartridge or capsule. The amount of fine powder discharged from the inhaler's mouthpiece during inhalation is largely dependent on, for example, interparticulate forces in the powder formulation and efficiency of the inhaler to separate those particles so that they are suitable for inhalation. One important inhaler characteristic is the ability of the inhaler to discharge effectively and repeatedly all of its powder content in order to deliver an accurate dose. Also the inhaler should be designed with internal conduits that avoid retaining powder and thus induce costly loss of the active agent to be delivered, which can be typical of, for example, amorphous and/or cohesive powders, and/or crystalline powders. Thus, the inhaler structural design must provide air conduits which effectively deliver the powder from its reservoir during use. The benefits of delivering drugs via the pulmonary circulation are numerous and can include rapid entry into the arterial circulation, avoidance of drug degradation by liver metabolism, ease of use, i.e., lack of discomfort of administration by other routes of administration.
Dry powder inhaler products developed for pulmonary delivery have met with limited success to date, due to lack of practicality and/or cost of manufacture. Some of the persistent problems observed with prior art inhalers, include lack of ruggedness, inconsistency in dosing, inconvenience of the equipment, poor deagglomeration, problems with delivery in light of divorce from propellant use, reduced powder discharge or loss of the powder due to powder retention within an inhaler, and/or lack of patient compliance. In some cases, efficient powder delivery from an inhaler is also dependent on the type of powder, i.e., crystalline versus amorphous powder. Certain types of amorphous powders tend to cake and smear while tumbling, which leads to a decrease inhaler emptying or deagglomeration efficiency and ultimately in drug delivery to a user. Therefore, an inhaler has been designed and manufactured with consistent powder delivery properties, which is easy to use without discomfort, and has discrete inhaler configurations which can allow for better patient compliance.